In one conventional technique for the manufacture of thin film integrated circuits, a relatively thin layer, typically 5,000 to 10,000A of patterned dielectric film is deposited on a slice of semiconductor material (p or n-type) to define those areas on the semiconductor slice where it is desired to generate semiconductor junctions. Typically, after diffusion of dopant material into the areas of the semiconductor slice (where there is no dielectric barrier) aluminum metal is vapor deposited over the entire surface area, followed by its patterning to establish ohmic contacts with the preselected semiconductor junctions. Subsequently a critical metal like copper or nickle is sputtered or vapor deposited over the entire surface area for the purpose of covering the exact underlying areas preliminarily covered by the aluminum layer. This operation requires precision photoresist masking followed by acid etching of the copper or nickel from undesired areas, subsequently followed by the removal of the remainder of the photoresist from the metal covered by it. In the prior art this photoresist stripping is accomplished by means of a digesting solvent that finitely oxidizes or degrades the underlying metal. It is to this metallic surface that high quality connecting leads are attached to enable contact with the outside world.
One of the difficulties associated with this particular technique arises from the inability to strip the residual masking photoresist without concomitant oxidation or degradation of the underlying metallic film. The utilization of wet photoresist strippers requires a post wet chemical treatment to restore oxide-free metallic surfaces; these reductants are of no practical value where chemical or physical degradation of the metal occurred, since any such phenomenon will manifest itself as variable surface conductivity yielding a faulty operation of the resultant integrated circuit. Additional drawbacks of the wet chemical approach involve, the contamination of the various solvents and their associated short shelf life, as well as the continuing cost coupled with their use and the inconvenience in rinsing and drying handling procedures prior to the diffusion step, the latter factor being one that ultimately reduces production yields.